In automobile engines, engine oil seals are used to prevent leakage of fluids such as engine oil to the outside from edge portions of crankshafts protruding from crank chambers of the engines.
Various vehicle engine oil seals have been proposed, and examples thereof include an oil seal disclosed in Patent Document 1. The oil seal is for use in engines and has a sealing lip portion formed of an elastomer composition containing a silica compound and an elastomer such as acrylic rubber (ACM), fluororubber (FKM), nitrile rubber (NBR), urethane rubber (U), silicone rubber, hydrogenated nitrile rubber, and blends of these. Here, Patent Document 1 discloses that preferable elastomers are ACM and FKM.
Patent Document 2 discloses an oil seal for use in engines which has a rubber lip portion formed of silicon rubber or fluororubber.
Moreover, Patent Document 3 discloses a method for forming a fluororesin coating on the rubber surface with an aim of decreasing the sliding resistance of a seal lip portion in an oil seal.
In recent years, improvement in sliding properties of vehicle engine oil seals is desired along with the demand for higher performance (higher rotations) and better fuel economy of automobile engines. For sure, a vehicle engine oil seal formed of fluororubber or silicon rubber is likely to have better sliding properties compared to a vehicle engine oil seal formed of acrylic rubber or nitrile rubber. The above-mentioned demand requires further improvement in sliding properties, that is, improvement in sliding properties over the entire rotation range of automobile engines from a low rotation range to a high rotation range.
Patent Document 1: JP 8-338533 A
Patent Document 2: JP 7-208610 A
Patent Document 3: JP 2006-292160 A